Add support for `!e`

[job]

From the docs:

!e<set_names> excludes set names from set resolving. During recursive resolving as part of !i and !a queries, sets with these names are not expanded. The list is comma-separated, e.g. !AS-EX1,AS-EX2. In addition, !e-lc returns the set names that are currently excluded. Exclusion does not apply when the target of the query is an excluded object, i.e. with the previous example, !aAS-EX1 is still resolved. The setting persists across queries.

https://irrd.readthedocs.io/en/stable/users/queries/whois/

This should optimize invocations like $ bgpq4 AS-SNIJDERS EXCEPT AS15562